How UV-Curable Ink Works
The research and development, and quality control in the manufacturing of inkjet ink is crucial to achieve the color consistency and print quality delivered by today’s production UV digital presses. Here is a closer look at the chemical components and processes involved that allow UV-curable ink to perform to these exacting standards.
The basic make-up of UV-curable inks consists of four components: monomers, oligomers, pigments, and photoinitiators.
The monomers provide a building block of the ink, and can contribute certain properties such as softness/hardness of the ink when cured, as well as flexibility or elongation characteristics of the ink for varying types of applications. Monomers also help control ink viscosity, which is essential to jetting reliability.
The oligomers in the ink formulation consist of reactive resins and uniquely formulated adhesive components for printing on a wide range of different substrates.
The pigments provide the color. However, the pigment dispersion is a critical component of the UV ink make-up, as the particles need to be ground to less than 200 nanometers (less than the diameter of a human hair) to fully develop color, with each nano particle coated to prevent agglomeration and potentially blocking an inkjet nozzle that would compromise jetting accuracy, resulting in unacceptable print quality. Essentially all inkjet inks need to be nano-sized to jet reliably, and provide precise drop placement to optimize print quality.
When the photoinitiators are exposed to UV light, the oligomers and monomers cross-link or polymerize. So unlike aqueous or water-based inks, no heat or air drying is required for curing. But even the photoinitiators need to be tuned to a specific wavelength of UV light so curing can be accomplished by UV or LED-UV lamps.
To learn more about UV-curable ink technology and how it is delivering print solutions to help printers win more branded work, visit Fujifilm (Booth 2013).